Farming Magazine - March, 2013
Forages: Early-Season Cropping Decisions
By now the snow should have melted, or at least be in the process of doing so, even in more northerly regions. Soon the first warm spring days will begin to green up fields, and when this starts happening, you should be out there checking alfalfa and other legume fields. Winter damage can result from several causes, including frost heaving, insects feeding on taproots and simple cold weather damage. If you find winter damage, it's important to determine the cause, because this may influence the actions you take.
Frost heaving is more common in young alfalfa stands, particularly seedings made late last summer. However, mature stands can also suffer frost heaving, and I've seen alfalfa plants heaved 3 inches out of the ground. Frost heaving fractures the plant's taproot, and even if the plant begins to green up and send out new shoots, it will die when it runs out of the nutrients stored in the remaining portion of the taproot. There's not a lot that can be done to prevent frost heaving, though site selection may help some. Light-textured, well-drained soils are less susceptible to frost heaving.
Is anything bugging your alfalfa?
Be on the lookout for alfalfa plants that, although they're alive, aren't doing nearly as well as other plants in the field. For instance, when the better plants are 6 inches tall, these plants are only 2 to 3 inches tall and often off-colored. Dig up a few of the affected plants and examine the taproot on each. Clover root curculio larvae feed on alfalfa taproots, and the easiest time to see the aboveground impact of this feeding is early spring, soon after the plants break dormancy. There's not a lot you can do to control this insect, but if you see significant taproot damage, you should put the affected field on your list of fields to be rotated to another crop in 2014. If damage is severe, earlier action may be necessary.
As troublesome as clover root curculios are, the damage they cause pales in comparison to that done by the alfalfa snout beetle, which (fortunately) is present in only a handful of counties in New York, primarily across the top of the state. This insect destroys taproots and can decimate an alfalfa field in one year. Many farmers in the affected regions have simply given up on growing alfalfa. However, thanks to the efforts of Cornell University entomologist Dr. Elson Shields, there's a "friendly" nematode available that kills snout beetle larvae - the first effective means of controlling this devastating insect. The nematode can be raised by farmers and then sprayed on fields. Indications are that the control resulting from this application should be very long-lived, since the nematodes will continue to live in the farmer's field, not affecting any beneficial insects. If you've never seen an alfalfa snout beetle on your farm, consider yourself lucky.
Early-season fertilizer decisions
Most alfalfa in the northeastern U.S. is seeded with a forage grass companion crop. Therefore, as the alfalfa declines in a field, at some point the decision will need to be made as to whether the field should continue to be managed as an alfalfa field or as grass. This is an important decision, because once the alfalfa becomes a relatively small portion of the forage, nitrogen fertilizer or manure should be applied early in the season.
Contrary to popular opinion, nitrogen or manure won't hurt the remaining alfalfa plants, but it can greatly increase grass yield and protein content. One of the nice discoveries farmers often make is how well a tired-out alfalfa-grass field yields when nitrogen or manure is applied soon after spring green-up. However, time is of the essence, which is why I much prefer nitrogen fertilizer to manure for early-season applications. It takes too long to apply manure, and because fields are soft this time of year, the spreader and tractor may rut up the field.
How much fertilizer or manure? This depends on how much grass is in the field, as well as the grass species, but in general I'd recommend about 50 pounds per acre of actual nitrogen. This is less than the 70 to 90 pounds per acre I usually recommend for straight grass stands, but remember you're fertilizing a mixed stand. The recommended manure rate would depend on the amount of nitrogen in the manure. You should have a fairly recent manure analysis, which would make the decision simple. Apply enough manure to wind up with about 50 pounds of nitrogen per acre, or perhaps a bit more, depending on how anxious you are to reduce your inventory of manure. Lacking a manure analysis, apply up to several thousand gallons of liquid or slurry manure per acre. I'd rather have you apply 2,000 gallons per acre and be able to cover all the fields that need it, instead of putting a lot on some fields and none on others.
Check inventories: It's probably been many months since you applied herbicides (if you do your own spraying), so you may not remember what products you have left and the quantity of each. Were liquid formulations stored properly over the winter, which in most cases means protecting them from freezing? If a liquid formulation did get frozen, check the label. If it was supposed to be protected from freezing but wasn't, shake the container to make sure it still appears to be OK. However, appearances can be deceiving, so if you're in doubt, call the number listed on the herbicide container. Someone in the technical assistance department of most major pesticide companies should be able to provide some advice.
Also check the expiration date on any leftover silage inoculants. Silage inoculants are living bacteria, and I'd much rather spend the money to buy a few packets of fresh inoculant than to apply something that won't do anything.
Do the same for farm seeds, and if in doubt about the viability of a particular seed lot, consider getting a germination test done on any in question. These tests aren't expensive, and I'd certainly have a questionable seed lot tested instead of simply discarding it, because some species will retain their viability for several years.
Check over both your grain drill or seeder and corn planter and make any needed repairs now, not when it's time to plant. There are few things more frustrating than to be waiting on a part for your corn planter when all your farming neighbors are in their cornfields.
Ev Thomas has worked as an agronomist in New York for 45 years. He has written our Forages column for 15 years and has been an expert contributor on a number of other topics.